The present invention relates generally to a tip assembly for a welding torch and, particularly, to a tip assembly for a wire feed welding system.
A common metal welding technique employs the heat generated by electrical arcing to transition a workpiece to a molten state, followed by addition of metal from a wire or electrode. One technique that employs this arcing principle is wire-feed welding. At its essence, wire-feed welding involves routing welding current from a power source into an electrode that is brought into close proximity with the workpiece. When the electrode is sufficiently close to the work piece, current arcs from the electrode to the workpiece, completing a circuit and generating sufficient heat to melt and weld the workpiece. Often, the electrode is consumed and becomes part of the weld itself. Thus, new wire electrode is advanced, continuously replacing the consumed electrode and maintaining the welding arc. If the welding device is properly adjusted, the wire-feed advancement and arcing cycle progresses smoothly, providing a good weld. One common type of wire-feed welding is metal inert gas or “MIG” welding.
In typical wire-feed systems, wire electrode is directed through a welding cable, into a torch assembly, and, lastly, into a contact tip housed within the nozzle assembly. Electrical current is routed from the cable to the wire electrode through the contact tip. When a trigger on the welding torch is operated, wire electrode is advanced toward the contact tip, at which point current is conducted from the contact tip into the egressing electrode.
Because of its proximity to the weld location, a contact tip is exposed to weld splatter and relatively high-levels of heat. Accordingly, contact tips require more frequent maintenance or replacement than other components of the welding system. To facilitate quick replacement of contact tips, present assemblies include certain “threadless” contact tip assemblies, in which the contact tip is not threaded with respect to the remainder of the torch assembly.
Unfortunately, there are a number of problems associated with existing threadless contact tip designs. As one example, the structures for binding the contact tip in the welding torch can impart bending stresses on the contact tip. As another concern, variations in the distance between the contact tip and the exterior portion of the nozzle, known as the tip-nozzle recess, occur with existing threadless contact tip designs. A consistent tip-recess distance is highly desireable in certain welding applications, especially robotic welding systems. In addition, molten spatter from the weld may deposit on the end of the nozzle, eventually requiring replacement of the nozzle. Consequently, nozzles having a nozzle body and a removable threaded end section have been developed. However, weld spatter may contaminate the threads or the threads may experience galling, requiring a tool, such as a wrench, to remove the threaded end section from the nozzle body.
Furthermore, to prevent the ingress of impurities into the molten weld, a flow a shielding material is typically provided to the weld location when certain types of wire electrode are employed. By way of example, inert shielding gas is routed from a gas source, through a welding cable and welding torch, into a gas-diffuser that delivers the gas to the weld location via a nozzle. Welding systems that employ such shielding materials are often referred to in the industry as gas metal arc welding (GMAW) systems, or MIG systems, as mentioned above.
However, there are certain other types of wire electrodes that are employed without a shielding gas. Accordingly, when employing such “gasless” electrodes, the gas routed into the welding cable is blocked from egressing to the environment. In the past, this meant replacing the components at the terminal end of the welding torch with those that prevent the egress of gas. For example, when using gasless wire electrodes, the diffuser is replaced with a component or components that seat the contact tip, prevent the egress of gas from the cable, and electrically insulate a user from the operating current in the contact tip.
Unfortunately, when a welder desires to use both types of electrode, transitioning between these terminal components can be a time consuming task. Moreover, existing arrangements accommodating the different electrode systems generally require an operator to maintain a relatively large inventory of parts, thus increasing the costs of operation.
Therefore, there exists a need for improved contact tip assemblies for welding devices, particularly for facilitating the transition between gas shielded and gasless welding.